NEUTRON REFLECTIVITY OF LI-6-TI MULTILAYER WITH A NI REFLECTOR APPLIED TO UCN DETECTOR

The neutron reflectivity of a Li-6-Ti multilayer mirror with a Ni refl ector at the base has been measured using a time-of-flight spectromete r and a reflectometer. The results show that the reflectivities rise t o 0.5 at 560 Angstrom, which corresponds to the Ni critical wavelength , decrease to 0.2 with increasing neutron wavelength, and then rise to wards unity at about 800 Angstrom. This implies that neutrons in wavel ength region between 560 Angstrom and 800 A penetrate through the Li-6 -Ti multilayer and are absorbed by Li-6. The application of the Li-6-T i multilayer to a neutron converter for an ultracold neutron detector is discussed.